The pathogenic fungus Cryptococcus neoformans has emerged as the primary cause of community acquired meningitis in regions of the world plagued by HIV infection. Our previous studies have demonstrated a role for post-transcriptional gene regulation in stress tolerance. Our long term goal is to systematically map the protein-RNA interactions that C. neoformans requires for the maintenance of stress tolerance and pathogenicity. We hypothesize that these RNA-protein interactions contribute to the adaptability of C. neoformans, conferring agility to gene expression independent of the nucleus. In this proposal, our focus is two-pronged: First we will identify the RNA binding protein that is interacting with a GGAUG cis element in ribosomal protein transcripts found up-regulated in the ccr4? mutant, and determine its role in stress tolerance and pathogenicity. Second, we will determine the role of the C. neoformans PUF family of RNA binding proteins in stress tolerance and pathogenicity. For both the GGAUG-binding protein and the PUF proteins, we will determine the complement of transcripts that interact with each, allowing us to assemble their respective RNA regulons. Future studies will then build on this work and expand to additional classes or RNA binding proteins. Ultimately, the identification of RNA-protein interactions important for C. neoformans stress tolerance and pathogenicity will provide us with specific targets for novel small-molecule based therapeutics.